Flow Property and Micellar Structures in Capillary Flows of Surfactant Solutions

This paper includes three topics of the unsteady flow analysis of viscoelastic fluids with both numerical and experimental methods, i.e. startup flows in channels, three-dimensional flows, and viscous fingering in Hele-Shaw cells. The first topic presents results of the numerical analysis of startup flows using the Leonov model and results of velocity measurements with laser Doppler velocimetry in abrupt contraction flows. The mechanism of transient change in velocity field was discussed in view of the relation to the stress field. In the second topic, the flow of polymer solutions in a rectangular channel with a cavity is considered. Results of flow visualization and the numerical simulation using the Phan-Thien Tanner model are shown. The relation between a three-dimensional flow in the cavity and elastic properties of viscoelastic fluids was found. Finally, in the third part, the unstable growth phenomenon of the interface between two fluids, viscous fingering, is treated. Some examples of anomalous behavior of fingers in surfactant solutions are presented.

“…32,33) These results suggest that the sudden protrusion relates to changes in micellar structure and rheological properties due to the flow.…”

Section: Growth Phenomenon Of Viscous Fingers In Polymer Solutions Anmentioning

confidence: 85%

Numerical and Experimental Analyses of Unsteady Viscoelastic Flow in Complex Flow Field

Yamamoto

2006

“…[7][8][9][10][11][12] Kadoma et al [7][8][9] observed the change of SALS pattern at various shear rates (simple shear flow) with various excess salt ratios (Y) to investigate its effect on flow-induced orientation and concentration fluctuations for CTAB/NaSal solutions. They reported the relationship between several multiconnected networks of micelles and the SALS patterns.…”

Section: 6)mentioning

confidence: 99%

“…Moreover, they tried to estimate the relaxation time using the SALS pattern and obtained good agreement with the data from mechanical rheological measurement. Hashimoto et al 10) conducted an experiment to investigate the development of micellar structures by examining the flow of CTAB/NaSal in a capillary rheometer. They found that the flow curve has a bending point, and shear thinning happens at high shear rate after the bending point.…”

Section: 6)mentioning

confidence: 99%

Experimental Study of Pressure Loss and Rheo-Optical Behavior of CTAB/NaSal Aqueous Solution under Elongational Flow

Ôkawara

Hasegawa

Yamada

et al. 2009

In a previous paper we clarified the behavior of pressure losses DP for aqueous solutions of cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal) in an elongation dominant flow through slots: the flow curves relating DP to the apparent elongational rate consisted of three characteristic regions. In particular, DP increased largely in a specific region II, and this characteristic was suggested to be closely connected to the flow induced structure (FIS). However, it could not be asserted that FIS solely causes the large increase in DP, because vortices were also found in the flow upstream of the slot in region II and such vortices are known to induce large pressure drops frequently. In the present experiment, we used a nozzle providing almost the same constant elongational rate as the slot in order to eliminate the influence of vortices on DP, estimated elongational rates of the upstream flow, compared DP for both the slot and the nozzle, and concluded that vortices existing in the region upstream of the slot do not give a significant effect on DP. Next, the image of small angle light scattering (SALS) was examined to clarify the developing process of FIS: A butterfly-type and streak-type combined pattern in SALS occurs in region II, indicating the generation of FIS; the streak-type pattern degenerate at higher elongational rates in region III, meaning a partial collapse of FIS generated in region II; change in FIS depends not only on strain rate but also on strain in elongational flow. Moreover it was found that FIS shows a step-like development in the upstream flow of constant elongational rate.

“…4) Our research group also has studied the flow of CTAB/NaSal solutions, e.g. the relation between flow properties and micellar structures in capillary flows 5) , unstable flow in an axisymmetric abrupt contraction channel 6) , viscous fingering 7) , and the relation between pressure loss and elongation property in flows through a packed bed of particles 8) . In these studies, it was found that the flow induced structure of micelles greatly affected the flow behavior of wormlike micelle solutions.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of Startup Flows of Wormlike Micellar Solutions in an Axisymmetric Capillary Channel using a Modified Bautista-Manero Model

Yamashita

Yamamoto

Hashimoto

2009

Self Cite

Startup flows of wormlike micellar solutions in an axisymmetric capillary channel were numerically studied using a modified Bautista-Manero (MBM) model as a constitutive equation. The values of model parameter of the MBM model decided for a CTAB/NaSal solution were employed. The velocity profile at steady state predicted by the numerical simulation agreed with corresponding experimental data. The present study treated startup flows at a constant pressure gradient, which corresponds to a stress-controlled-type flow. The flow rate increased with time until the flow reached a steady state. The velocity profile had an inflection point around which the velocity gradient rapidly changed. The position of inflection point slightly changed with time. Temporal changes in both fluidity and the micellar contribution to shear stress occurred within a wall side region of the inflection point, where a white turbidity phenomenon was observed in our previous experiments. These temporal responses are characteristic of the startup flow at constant pressure gradients.